Cisco 2511 wireless route with dialup backup

[sigipa]

Hi,

I'm trying to set up a cisco 2511 so that it will use a wireless link as the primary route and a dial up link as the backup. I have read a couple of other posts on the general topic of backup routes, but I'm having a bit od trouble getting this to work. Here's my setup

I have two 2511s which are currently connecting two locations via dialup link. I have a linux router that provides internet access and a vpn between both offices. The 2511s are the primary routers. I want to leave the 2511s as the primary routers and setup static routes to both the internet and the dialup link. The internet (vpn) would be the primary route with the dialup link as a backup. I have tried the following.

Router A
ip route 0.0.0.0 0.0.0.0 192.168.1.253 (internet)
ip route 192.168.4.0 255.255.255.0 192.168.1.253 1 (vpn)
ip route 192.168.4.0 255.255.255.0 Async1 2 (dialup)

Router B
ip route 0.0.0.0 0.0.0.0 192.168.4.253 (internet)
ip route 192.168.1.0 255.255.255.0 192.168.4.253 1 (vpn)
ip route 192.168.1.0 255.255.255.0 Async1 2 (dialup)

Based on what I've read this should work, but doesn't. Could anyone tell me where I'm going wrong?

Thanks,
-S